Western British Columbia Research Articles

EVOLUTIONARY GENETICS AND PLEISTOCENE BIOGEOGRAPHY OF NORTH AMERICAN TREE SQUIRRELS (TAMIASCIURUS)

Nucleotide sequence data from the mitochondrial DNA (mtDNA) cytochrome-b gene and allozymic data were used to infer the evolutionary and biogeographic histories of New World tree squirrels of the genus Tamiasciurus. Phylogenetic analyses of the cytochromeb data support the existence of 3 mtDNA lineages within Tamiasciurus: a western lineage consisting of populations of T. douglasii from western British Columbia (Canada), Washington, Oregon, and California, and T. mearnsi from northern Baja California (Mexico); a southwestern lineage consisting of populations of T. hudsonicus from New Mexico and Arizona; and a geographically widespread lineage comprising populations of T. hudsonicus from the remainder of the species’ range. Levels of mtDNA sequence variation observed within and among populations of Tamiasciurus were small (0‐2.4%), suggesting that contemporary geographic patterns of genetic variation in Tamiasciurus have been established relatively recently (i.e., in the Late Pleistocene). Allozyme analyses also support a close relationship among extant populations of Tamiasciurus. No fixed allelic differences were observed among the 3 recognized species and interspecific genetic distances (Nei’s D) were substantially less than those typically observed between sibling species. Although differing from the current taxonomy in several respects, geographic patterns of genetic variation observed within Tamiasciurus are similar to those observed in a variety of North American boreal forest taxa and most likely reflect effects of forest fragmentation associated with glacial cycles of the Pleistocene.

Characteristics of terrain, snow supply and forest cover for avalanche initiation caused by logging

AbstractThis paper contains statistical analyses of parameters to characterize starting zones of destructive avalanches which have resulted from clear-cut logging in British Columbia, Canada. Data from 76 avalanche sites in the Coast Mountains (western British Columbia) and the Columbia Mountains (eastern British Columbia) are analyzed. The parameters include a selection which characterize snow supply (related to potential avalanche frequency), avalanche magnitude and those which are known to affect avalanche formation including terrain features, vegetation density, vegetation height and ground surface roughness. The results provide the data framework for possibly preventing future disasters by altering logging plans.

Kinematics and tectonic significance of transpressive structures within the Coast Plutonic Complex, British Columbia

Structural data from the Coast Plutonic Complex, near Prince Rupert, British Columbia, are consistent with a deformational history dominated by dextral transpression from Campanian to Paleocene time. Penetrative east-side-up, southwest-directed, ductile shearing produced moderately northeast-plunging overturned kilometer-scale isoclinal folds. These folds are dextrally sheared and refolded into kilometer-scale upright northwest-plunging folds and steeply dipping transposed foliations with moderate to shallow northwest-plunging lineations along their western side. An east-side-up component to the transcurrent shearing is kinematically compatible with east-side-up shearing found within the Great Tonalite Sill. Kinematic and geometric gradients and the spatial distribution of the finite stretching direction are interpreted to result from partitioning of transpression. The location of these structures and overprinting relationships suggest the Great Tonalite Sill intruded late-kinematically into a crustal-scale dextral transpressive shear zone. These results indicate this shear zone could form part of the Baja-B.C. fault system that would have accommodated large northward displacements of the terranes making up western British Columbia and southeast Alaska. This conclusion is based on: (1) It is favorably located to accommodate the proposed displacements; (2) Deformation occurred during the time period of proposed large displacement (83–59 Ma); (3) The 15-km thickness of the shear zone indicates it records large displacements.

Wide-angle seismic imaging across accreted terranes, southeastern Alaska and western British Columbia

This study addresses the question of crustal, Moho, and uppermost mantle structure across an accreted terrane, continental arc, and fold and thrust belt in southeastern Alaska and western British Columbia. The 186-km-long Portland Canal line of the ACCRETE wide-angle seismic dataset across the Coast Mountains is analyzed using a combination of travel-time analysis techniques, including delay-time tomography, turning ray tomography, reciprocal time analysis, intercept-time inversion, and forward ray tracing. Additional constraints on the model are obtained from a coincident vertical-incidence seismic section and from correlation with the mapping of geologic structures plunging into the seismic section. The study reveals moderately high crustal velocities, low-velocity gradient in the middle crust, and decreasing average crustal velocity and a north-deepening Moho. Termination of crustal reflectivity across a vertical zone (the Coast Shear Zone, CSZ) indicates that the CSZ is most likely a strike-slip fault associated with a transpressive tectonic regime. A mid-Cretaceous thrust system mapped on the surface to the west of the CSZ is imaged by several groups of mid- to lower crustal reflectors extending close to the Moho indicating it was a thick-skinned thrust system. NE-dipping fabric imaged within the Coast Mountains batholith (CMB) is associated with a ductile deformation during Early Eocene crustal extension. The crustal section under the CMB, which has an average velocity of 6.55 km/s and shallower than average crustal thickness of 31 km, can be considered as corresponding to the lower two thirds of an average crustal section which has been inflated by intrusions of high-velocity tonalite to gabbro sills.

Mountain Plants of the Pacific Northwest: A Field Guide to Washington, Western British Columbia and Southeastern Alaska, by r. J. Taylor and G . W. Douglas [Review

Mountain Plants of the Pacific Northwest: A Field Guide to Washington, Western British Columbia and Southeastern Alaska, by r. J. Taylor and G . W. Douglas [Review

Enantiospecific pheromone production and response profiles for populations of pine engraver,Ips pini (Say) (Coleoptera: Scolytidae), in British Columbia

Analyses of the enantiomeric composition of ipsdienol produced by individual male pine engravers,Ips pini (Say), from six populations in British Columbia, support the hypothesis that New York and Idaho races of this species hybridize in southeastern British Columbia. Production profiles, expressed as frequency distributions of (+):(-) ipsdienol ratios [= ratio of (S)-(+)-ipsdienol to (R)-(-)-ipsdienol], were bimodal for four western British Columbia populations. The (+):(-) ratios ranged from 63:37 to 71:29. consistent with those previously found for the New York race. The profile for a southeastern population from Radium, British Columbia, was intermediate between those for the four western British Columbia populations and that from one population in Kimberley, British Columbia, just south of Radium. Males in the Kimberley population produce predominantly (R)-(-)-ipsdienol, typical of California nad Idaho males. Response profiles of different individuals ofI. pini, determined by captures of beetles in multiple-funnel traps baited with ipsdienol of 11 different (+):(-) ratios, were not consistent with production profiles. Populations in Williams Lake and Princeton, in western British Columbia, and Radium, in southeastern British Columbia, had response profiles with maximal attraction to ipsdienol over a broad range of (+):(-) ratios, falling off as enantiomeric purity was approached at either end of the spectrum. This type of response profile is consistent with that for the New York race, which has been shown to respond optimally to (+):(-) ratios ranging from 40:60 to 70:30. The response profile of the Kimberley population gradually declined from maximal attraction to ipsdienol with a (+):(-) ratio of 2:98 to the lowest response at a (+):(-) ratio of 98:2. The attraction ofI. pini to chemical stimuli in California is interrupted by ipsdienol with a (+):(-) ratio >5:95, a pheromone of a host competitor, the California five-spined ips,Ips paraconfusus Lanier. We hypothesie that the Idaho race, which does not compete withI. paraconfusus due to geographical separation, is characterized by a Kimberley-type enantiomeric response profile, intermediate between those of the New York and California races.

Mountain plants of the Pacific Northwest: a field guide to Washington, Western British Columbia, and Southeastern Alaska

Mountain plants of the Pacific Northwest: a field guide to Washington, Western British Columbia, and Southeastern Alaska

Hit-and-run collision model for the Laramide orogeny, western United States

The formation of the Rocky Mountains, an event referred to as the Laramide orogeny, has presented a dilemma since the introduction of plate tectonics. In scale and tectonic style, the Late Cretaceous–early Tertiary orogeny resembles collisional orogenies such as the Himalayas. However, no collider remains adjacent to the continental margin at the latitude of Laramide features (i.e., California to Washington). Terranes of western British Columbia and southeast Alaska, known together as “Baja BC,” may constitute the colliding plate. Geologic studies and paleomagnetic data suggest that Baja BC collided with North America at the latitude of modern Baja California (the “hit”) and was subsequently translated northward during oblique convergence (the “run”) to its present latitude between 94 Ma and ca. 40 Ma. Northward translation of Baja BC is spatially and temporally coincident with the ca. 80 to 45 Ma Laramide orogeny, suggesting a causal link between the events.

Evolution of the eastern Waddington thrust belt and its relation to the mid‐Cretaceous Coast Mountains arc, western British Columbia

The eastern Waddington thrust belt cuts the eastern margin of the Coast Mountains mid‐Cretaceous magmatic arc. Thrust faults carried Triassic rocks of the Intermontane superterrane, Early Cretaceous volcanic and clastic rocks, and volcanic and plutonic rocks of the active arc to the northeast, outward from the core of the arc. Minimum shortening across the thrust belt is estimated as 50% or 40 km. Synkinematic through postkinematic metamorphism produced an inverted metamorphic gradient with the structurally higher magmatic arc as the likely heat source. Radiometric, thermochronologic, and structural data indicate that the thrust belt was active at 84 Ma and probably at 87 Ma and suggest that the peak of postkinematic metamorphism occurred about 82–84 Ma. The thrust belt was intruded by postkinematic plutons in latest Cretaceous and early Tertiary time (68 Ma and 58 Ma). The eastern Waddington thrust belt is coeval with or slightly younger than a system of west directed thrusts in the western and southern parts of the Coast Mountains arc. The prominence of these structures suggests that synmagmatic contraction played a major role in development of the arc. The distribution and character of syn‐and postthrusting metamorphism indicate that this contraction, rather than localized loading by magma, produced the metamorphism.

Fission‐track ages of detrital zircons from Cretaceous strata, southern British Columbia: Implications for the Baja BC hypothesis

The Methow/Tyaughton basin contains a thick sequence of mid‐Cretaceous (Albian‐Cenomanian) marine clastic sediments, which have been interpreted as synorogenic fill deposited during collision and accretion of the Insular superterrane at the North American margin. Three distinct, regionally extensive petrofacies have been recognized in this sequence: (1) a west‐derived volcanic petrofacies, (2) a cherty petrofacies derived from a local intrabasinal high, and (3) an east‐derived arkosic petrofacies. Grain ages for detrital zircon are used here to identify provenance. The fission track (FT) method is used to date seven sandstone samples, with ∼45 grain ages per sample. Grain age distributions show marked differences between petrofacies and close similarities within a petrofacies. All petrofacies are dominated by a young population of grain ages (113 to 89 Ma), statistically indistinguishable from the depositional ages of the samples. This population is attributed to contemporaneous volcanism in the source region. The age of older populations varies among the petrofacies, indicating that each petrofacies was derived from different source terrains. Most important, all Arkosic samples have nearly identical grain age distributions, even though they come from widely separated parts of the Methow/Tyaughton basin. This evidence suggests that the Arkosic petrofacies is an overlap sequence that ties together disparate basement terranes, including the Bridge River, Cadwallader, and Methow terranes, by the Albian (∼100 Ma). The source of the Arkosic petrofacies provides an important constraint on the mid‐Cretaceous location of these outboard terranes. This petrofacies increases in thickness and coarseness to the east, suggesting a source inboard of the Methow/Tyaughton basin. The detrital composition of the sediment indicates that high‐grade metamorphic rocks and S‐type plutonic rocks were present in the source. Given the rapid onset of arkosic sedimentation in the Albian, we infer that this petrofacies was derived from newly uplifted metamorphic and plutonic rocks. We consider two interpretations for this arkosic source. An in situ interpretation would derive these sediments from metamorphic and plutonic rocks of the Omineca Crystalline belt, which presently lies to the east of the basin. The onset of arkosic sedimentation during the Albian is compatible with evidence from the Alberta foreland basin that indicates Albian uplift and denudation of the Omineca Crystalline belt. However, Nd/Sm data from the Arkosic petrofacies (Barfod and Nelson, 1992) indicate a fairly primitive source, which is not consistent with the presence of Precambrian rocks in the Omineca belt. The second interpretation accounts for paleomagnetic data that indicates the outboard terranes of western British Columbia have been transported 3000 km northward during the latest Cretaceous and early Tertiary. In this case, the arkosic sediments would most likely have been derived from an inboard continental setting near the present‐day latitude of central Mexico. A possible source might have been the western half of the Peninsular Ranges batholith, which is characterized by plutonic rocks with relatively primitive isotopic characteristics.

A Coast Mountains provenance for the Valdez and Orca groups, southern Alaska, based on Nd, Sr, and Pb isotopic evidence

Nd, Sr, and Pb isotopic data were obtained for fourteen fine- to coarse-grained samples of accreted flysch of the Late Cretaceous and early Tertiary Valdez and Orca Groups in southern Alaska to determine the flysch provenance. Argillites and greywackes from the Orca Group, as well as compositionally similar but higher metamorphic grade rocks from the Valdez Group, show a restricted range of correlated ε Nd ( −0.6 to −3.8) and 87Sr/ 86Sr (0.7060–0.7080) at the time of sediment deposition ( ∼ 50 Ma). Pb isotopic compositions also vary over a narrow range ( 206Pb/ 204Pb= 19.138–19.395, 207Pb/ 204Pb= 15.593–15.703, 208Pb/ 204Pb= 38.677–39.209), and in the Orca Group the samples generally become more radiogenic with decreasing ε Nd and increasing 87Sr/ 86Sr. All samples have similar trace element compositions characterized by moderate light rare earth element enrichments, and low ratios of high field strength elements to large ion lithophile elements. Based on petrographic, geochemical, and isotopic data the sedimentary rocks are interpreted to have been derived largely from a Phanerozoic continental margin arc complex characterized by igneous rocks with ε Nd values between 0 and −5. The latter conclusion is supported by the ε Nd values of a tonalite clast and a rhyodacite clast in the Orca Group ( ε Nd = −4.9and−0.9, respectively). However, trondjemitic clasts in the Orca Group have significantly lower ε Nd ( ∼ −10) and require a derivation of a portion of the flysch from Precambrian crustal sources. The Nd, Sr, and Pb isotopic compositions of both the Valdez and Orca Groups overlap the values determined for intrusive igneous rocks exposed within the northern portion of the Late Cretaceous to early Tertiary Coast Mountains Plutonic Complex in western British Columbia and equivalent rocks in southeastern Alaska. The isotopic data support previous conclusions based on geologic studies which suggest that the flysch was shed from this portion of the batholith, and from overlying continental margin arc-related volcanic rocks, following its rapid uplift in the Late Cretaceous and early Tertiary. The Precambrian crustal material present in the flysch may have been derived from Late Proterozoic or older metasedimentary and metaigneous rocks now exposed along the western margin of the Coast Mountains Plutonic Complex.

Neoglacial Glacier Fluctuations in the Canadian Rockies

The Little Ice Age was the most extensive Neoglacial glacier advance in the Canadian Rockies. Evidence of earlier, less-extensive Neoglacial glacier advances is based on wood recovered from several glacier forefields. Wood flushed out of Athabasca Glacier (7550-8230 yr B.P., three dates) and Dome Glacier (6120-6380 yr B.P., two dates) indicates that forests occurred upvalley of present glacier termini during the Hypsithermal. Detrital logs from Peyto (14 dates), Saskatchewan (3 dates), Robson (3 dates), and Yoho (1 date) Glaciers, plus in situ slumps at Peyto and Robson Glaciers, have yielded 14 C dates between 2490 and 3300 yr B.P. (12 dates between 2800 and 2990). This wood is derived from sources at or upvalley from present glacier termini and represents forests overridden by glaciers between ca. 3100 and 2500 yr B.P. (Treeline was higher than present immediately prior to this advance.) This advance, which did not extend beyond the Little Ice Age maximum position, is designated the Peyto Advance and correlated with the Tiedemann Advance in western British Columbia. Earliest Little Ice Age advances at Peyto and Robson Glaciers are dated ca. 800-600 yr B.P. at positions ca. 500 m upvalley from Little Ice Age limits.

Generalized versus site-specific biomass regression equations for Pseudotsuga menziesii var. menziesii and Thuja plicata in Coastal British Columbia

Site-specific biomass regression equations developed for Pseudotsuga menziesii var. menziesii and Thuja plicata by destructive sampling of individual trees in southwestern British Columbia were compared to generalized equations developed from the large data-set of Standish et al. (Standish, J.T., Manning, G.H. & Demaerschalk, J.P., 1985, Development of biomass equations for British Columbia tree species. Report BC-X-264, Canadian Forestry Service, Victoria, BC) for trees growing over a wide geographic area in western British Columbia. In the case of Psedutsuga, equations developed for trees growing on poor sites were also compared to those for trees growing on good sites. For Pseudotsuga, both geographical and site-specific variations in tree growth significantly influenced the parameters in biomass regression equations. These influences are likely to be most noticeable for sites exhibiting extremely low productivity. For Thuja, geographical variations also significantly influenced the parameters in biomass regression equations.

Coast Plutonic Complex: A mid-Cretaceous contractional orogen

Early Late Cretaceous east-vergent thrusts deform much of the eastern margin of the Coast Plutonic Complex in western British Columbia. Similarities in timing and style suggest that the faults represent a system of backthrusts to a west- vergent thrust belt on the west side of the complex. This geometry and the rarity of mid-Cretaceous strike-slip faults indicate that the Coast Plutonic Complex was a strongly contractional orogen in mid-Cretaceous time.

Genetic variation and productivity of Populustrichocarpa and its hybrids.: IV. Performance in short-rotation coppice

Resprouting after harvest and rapid growth of sprouts are often considered essential for success of close-spaced, short-rotation cultural systems. This study examined resprouting, subsequent growth, and dry weight production following the initial 4-year harvest of a "common garden" trial of 50 clones of Populustrichocarpa Torr. & Gray. The clones were selected from 10 populations (sources) from major river drainages from western British Columbia, Washington, and Oregon. Additionally, three P. trichocarpa × P. deltoides (Bartr.) hybrids, a 'Robusta' clone, and a previously selected P. trichocarpa clone from Cottage Grove, Oregon, were included in the experiment. Mean yield of P. trichocarpa clones was 11.3 Mg•ha−1•year−1 (CV among clones = 61%) in the coppice rotation vs. 12.6 Mg•ha−1•year−1 (CV among clones = 40%) in the initial rotation; a difference that may, at least in part, be due to the use of less fertilizer in the coppice rotation. Nevertheless, a number of clones including the hybrids had higher yields in the coppice than in the initial rotation. Yield of clones in the coppice rotation was only moderately correlated with yield in the initial harvest (r2 = 0.48), but the same two clones, hybrids 11-11 and 11-05, were the top-producing clones in both rotations. Cumulative mortality of P. trichocarpa at the end of the experiment, including failed cuttings, averaged 36%, but was highly variable (range = 7–66% among clones). Yield in both harvests differed significantly among sources of P. trichocarpa. As with other components of productivity reported earlier, performance in coppice varied significantly among the 50 P. trichocarpa clones, and more so than in the first rotation. Populustrichocarpa clones identified as superior in coppicing in this experiment represent potential parents for new hybrids intended for short-rotation systems involving coppicing.

Nutrient values in indigenous wild plant greens and roots used by the Nuxalk people of Bella Coola, British Columbia

Nutrient compositions of green leaves or roots from 18 different species of wild plants used by native Indian people of Western British Columbia, Canada, are given. Proximate composition including ash, moisture, fat, and protein and values for total carbohydrate and approximate energy are computed. Neutral detergent fiber is also reported. Values are given for calcium, phosphorus, sodium, magnesium, iron, zinc, copper, manganese, and strontium and for the vitamin determinations for thiamine, riboflavin, niacin, ascorbate, carotene, and folate. This is the first comprehensive nutrient report for most of these species of greens and roots, and the first report of any nutrient data on the roots of Lupinus nootkatensis and Polypodium glycyrrhiza. Also presented are data for the inner bark of Populus trichocarpa and the fruit of Pyrus fusca. It is the first report of strontium, folate, and neutral detergent fiber for any species of wild plant greens or roots used by Indian people of Western British Columbia.

The moss genus Dicranodontium (Dicranaceae) in Canada

A study of herbarium specimens of Dicranodontium was undertaken to facilitate the identification of the taxa present in Canada and to document their occurrence in the country. Keys, descriptions, illustrations, and distribution maps are provided for the four species in Canada, namely D. asperulum (Mitt.) Broth., D. denudatum (Brid.) Britt. in Williams, D. subporodictyon Broth., and D. uncinatum (Harv.) laeg. & Sauerb. One species, D. denudatum, has a disjunct distribution, being known from western British Columbia and southern Québec and Newfoundland. The other three species are known only from western British Columbia, predominantly the Queen Charlotte Islands. The rarity and restricted occurrence of these species is apparently due to the low sporophyte production resulting from the sterility of the majority of plants and to their preference for oceanic habitats. Only two species, D. asperulum and D. uncinatum, were seen with sporophytes.

Nutrient values in indigenous wild berries used by the nuxalk people of bella coola, British Columbia

The nutrient composition for 23 different species of wild berries used for food by native Indian people of Western British Columbia, Canada, are reported. Proximate composition includes moisture, protein, lipids, ash, and computed carbohydrate and energy values. Neutral detergent fiber values are given. Mineral values are given for calcium, phosphorus, sodium, magnesium, iron, zinc, copper, manganese, and strontium. Vitamin determinations are given for thiamine, riboflavin, niacin, ascorbate, carotene, and folate. This is the first comprehensive report for any of these species and the first report of any nutrient data in edible portions of Cornus canadensis, Ribes bracteosum, Ribes laxinorum, Shepherdia canadensis, Vaccinium alaskense, and Vaccinum membranaceum. It is the first report on strontium, folate, and neutral detergent fiber in edible wild berries of the west coast of North America.

Depositional History of Upper Triassic Carbonate Platforms on Wrangellia Terrane, Western British Columbia, Canada: ABSTRACT

Upper Triassic (Karnian-Norian) limestones of the Quatsino Formation, Vancouver Island, and the Kunga Formation, Queen Charlotte Island, were deposited within a complex rifted island arc system, which was accreted to the western margin of North America as Wrangellia during the mid-Cretaceous. Carbonates sedimentation began after a transgressive event submerged the subaerially exposed Karmutsen volcanics. In both Vancouver and Queen Charlotte Islands, the lower part of the carbonate sequence records the widespread development of a shallow, subtidal platform composed mainly of two facies: open-platform deposits (bioturbated fossiliferous wackestones) and platform sand-shoal deposits (oolitic-bioclastic grainstones). This early depositional stage evolved gradually into a second stage characterized by the fragmentation of the platform and development of a carbonate bank/basin topography controlled by extensional tectonics within Wrangellia. The interior facies of these carbonate banks consist of cyclic subtidal lagoonal and tidal-flat limestones, each cycle commonly capped by a vadose diagenetic layer. The bank margin facies comprises exclusively high-energy, oolitic sandshoal deposits. The adjacent basin facies include (1) pelagic/hemipelagic limestones, (2) platform-derived and slope-derived carbonate breccia, and (3) proximal to distal carbonate turbidites. In both island systems, carbonate sedimentation ended abruptly when the isolated carbonate banks were drowned and covered by basinal clastics in responsemore » to rapid subsidence probably caused by tectonic activity within Wrangellia.« less

Terrestrial heat flow above the Andean Subduction Zone in Bolivia and Peru

We report 35 new and 9 revised terrestrial heat flow measurements overlying the Andean subduction zone in Bolivia and Peru. The measurement sites are distributed in the Andean Cordillera, the Altiplano, the sub‐Andean ranges, and the sedimentary platform and basins to the east of the Andes. They fall in the distance range 75–900 km from the Peru‐Chile trench. Sites in the Peruvian Cordillera have a mean heat flow of 41 mW m−2, whereas those in the Bolivian Cordillera and Altiplano average 84 mW m−2. The sub‐Andean ranges and the adjacent sedimentary platform have a mean heat flow of 50 mW m−2. The higher heat flow of the Bolivian Cordillera and Altiplano lies to the east of Quaternary volcanoes along the Bolivia‐Chile border and in southernmost Peru and thus can be recognized as a “back arc” heat flow high. Neither Quaternary volcanism nor high heat flow are present in central and northern Peru. This contrasting along‐strike pattern correlates with the variable angle of subduction of the Nazca plate beneath the region. Beneath Bolivia the subduction is at about 30°–35°, whereas beneath Peru it is subhorizontal and may be providing a cold underplate to the overlying Peruvian lithosphere. Extensive Miocene volcanism in Peru suggests, however, that heat flow in Peru 10 Ma ago was likely similar to that in Bolivia in the present day and implies a change in subduction and a rapid diminution of heat flow in Peru over the past 10 Ma. Imbrication of cold oceanic lithosphere beneath Peru, analogous to that beneath western British Columbia, may provide a mechanism for rapid reduction of the heat flow.